Medium-induced gluon branching

A bstractWe study the evolution of an energetic jet which radiates gluons while propagating through a dense QCD medium modeled as a random distribution of color sources. Motivated by the heavy ion experimental program at the LHC, we focus on the medium induced radiation of (relatively) soft gluons, which are abundantly emitted at large angles and thus can transport a small fraction of the jet energy far away from the jet axis. We perform a complete calculation of the medium-induced gluon branching in the regime where the gluons that take part in the branching undergo multiple soft scattering with the medium. We extend the BDMPSZ theory of radiative energy loss by including the transverse momentum dependence in the kernel that describes the branching and by analyzing the correlations between the two offspring gluons. We demonstrate that these gluons lose color coherence with respect to each other over a time scale that is comparable to the duration of the branching. It follows that interference effects between successive emissions are suppressed, a necessary ingredient for a description of multiple emission of soft gluons by a probabilistic, branching process.

[1]  Y. Dokshitzer,et al.  Radiative energy loss of high-energy quarks and gluons in a finite volume quark - gluon plasma , 1997 .

[2]  Dominique Schiff,et al.  'Bottom up' thermalization in heavy ion collisions , 2001 .

[3]  F. T. Collaboration,et al.  Probing medium-induced energy loss with direct jet reconstruction in p+p and Cu+Cu collisions at PHENIX , 2009, 0907.4725.

[4]  Urs Achim Wiedemann,et al.  Gluon radiation off hard quarks in a nuclear environment: opacity expansion , 2000, hep-ph/0005129.

[5]  Russian Federation.,et al.  Fully quantum treatment of the Landau-Pomeranchik-Migdal effect in QED and QCD , 1996 .

[6]  C. Salgado,et al.  Q-PYTHIA: a medium-modified implementation of final state radiation , 2009, 0907.1014.

[7]  P. Lévai,et al.  Non-Abelian energy loss at finite opacity. , 2000, Physical review letters.

[8]  A. Mueller.  On the multiplicity of hadrons in QCD jets , 1981 .

[9]  F. Gelis,et al.  High energy pA collisions in the color glass condensate approach I: gluon production and the Cronin effect , 2004, hep-ph/0402256.

[10]  V. Fadin,et al.  Log - Log Asymptotic Form of Exclusive Cross-Sections in Quantum Chromodynamics , 1981 .

[11]  M. Gyulassy,et al.  Reaction operator approach to non-abelian energy loss , 2000, nucl-th/0006010.

[12]  Y. Dokshitzer,et al.  Radiative energy loss and p⊥-broadening of high energy partons in nuclei , 1997 .

[13]  C. Salgado,et al.  Antiangular ordering of gluon radiation in QCD media. , 2010, Physical review letters.

[14]  S. Salur.  First direct measurement of jets in $\sqrt{s_{\mathit {NN}}}=200~\mbox{GeV}$ heavy ion collisions by STAR , 2008, 0809.1609.

[15]  S. H. Kim,et al.  Suppression of charged particle production at large transverse momentum in central Pb – Pb collisions at √ sNN = 2 . 76 TeV ✩ , 2010 .

[16]  Andrea Benaglia,et al.  Jet momentum dependence of jet quenching in PbPb collisions at sNN=2.76 TeV , 2012 .

[17]  S. Salur.  First direct measurement of jets in √ sNN = 200 GeV heavy ion collisions by STAR , 2009 .

[18]  C. Salgado,et al.  The radiation pattern of a QCD antenna in a dilute medium , 2011, Journal of High Energy Physics.

[19]  Urs Achim Wiedemann.  Jet quenching versus jet enhancement: a quantitative study of the BDMPS-Z gluon radiation spectrum , 2001 .

[20]  Laurence G. Yaffe,et al.  Photon and gluon emission in relativistic plasmas , 2002 .

[21]  Guy D. Moore,et al.  Energy loss of leading partons in a thermal QCD medium , 2005 .

[22]  V. Khoze,et al.  Basics of Perturbative QCD , 1991 .

[23]  B.G.Zakharov.  Fully quantum treatment of the Landau--Pomeranchuk--Migdal effect in QED and QCD , 1996, hep-ph/9607440.

[24]  S. Jeon,et al.  MARTINI : An event generator for relativistic heavy-ion collisions , 2009, 0909.2037.

[25]  Transverse momentum dependence of the Landau-Pomeranchuk-Migdal effect , 1999, hep-ph/9906257.

[26]  J. Putschke.  First fragmentation function measurements from full jet reconstruction in heavy-ion collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV by STAR , 2008, 0809.1419.

[27]  Laurence G. Yaffe,et al.  Photon emission from quark-gluon plasma: complete leading order results , 2001 .

[28]  B. G. Zakharov.  Radiative energy loss of high-energy quarks in finite-size nuclear matter and quark-gluon plasma , 1997 .

[29]  C. Salgado,et al.  Jets in QCD media: From color coherence to decoherence , 2011, 1102.4317.

[30]  G. Parisi,et al.  Asymptotic Freedom in Parton Language , 1977 .

[31]  High Energy pA Collisions in the Color Glass Condensate Approach , 2006, hep-ph/0609258.

[32]  G. Marchesini,et al.  Jet Multiplicity and Soft Gluon Factorization , 1982 .

[33]  C. Salgado,et al.  The radiation pattern of a QCD antenna in a dense medium , 2012, Journal of High Energy Physics.

[34]  E. Iancu,et al.  Interference effects in medium-induced gluon radiation , 2011, 1105.1760.

[35]  J. Stachel,et al.  A local Monte Carlo framework for coherent QCD parton energy loss , 2011, 1103.6252.

[36]  Yu.L. Dokshitzer,et al.  Medium-induced radiative energy loss; equivalence between the BDMPS and Zakharov formalisms , 1998 .

[37]  Laurence G. Yaffe,et al.  Photon Emission from Ultrarelativistic Plasmas , 2001 .

[38]  C. Collaboration,et al.  Observation and studies of jet quenching in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV , 2011, 1102.1957.

[39]  Serguei Chatrchyan,et al.  Observation and studies of jet quenching in PbPb collisions at {radical}(s{sub NN})=2.76 TeV , 2011 .

[40]  R M Buckingham,et al.  Observation of a centrality-dependent dijet asymmetry in lead-lead collisions at sqrt[S(NN)] =2.76 TeV with the ATLAS detector at the LHC. , 2010, Physical review letters.

[41]  Dominique Schiff,et al.  Quenching of hadron spectra in media , 2001 .